The present invention is directed to a water gun and more particularly, to a water gun having a pressure chamber into which water is pumped and held under pressure for release from the water gun.
Toy water guns are known which utilize pressurized air or a pressurized bladder as the motive force for discharging water from the gun upon release of a nozzle valve. U.S. Pat. No. 4,135,559 describes a water toy and fill valve combination. The water toy includes a resiliently expandable tubular bladder which serves as the pressurized water reservoir and the motive member for discharging water from the gun. Pressurized water is loaded into the bladder via the fill valve combination such that the bladder expands due to water pressure of the water from the fill valve. A trigger is provided which is connected to a release valve is provided for allowing water to be ejected from the toy water gun.
U.S. Pat. No. 5,799,827 discloses a similar water gun having a tubular bladder arranged in a tubular holding member. A separate water tank is located on the gun which holds water at ambient pressure. A pump located on the gun is utilized to transfer water from the ambient pressure water tank into the bladder, expanding the bladder. Upon release of a nozzle valve, water is ejected from the toy gun.
U.S. Pat. No. 5,878,914 discloses a similar toy water gun utilizing a water tank with water at ambient pressure, a pump and a balloon-shaped bladder located in a bladder chamber. Specialized valving means are provided to allow air drawn in to the pump from the water reservoir to be pumped back into the reservoir instead of the bladder. An alternate type of pressure chamber is also described in which the pressure chamber is formed by a spring-loaded wall which can be compressed within a chamber.
A drawback with these types of arrangements is that it is difficult and costly to produce a tubular or balloon-shaped bladder economically and with the desired characteristics to provide for fluid discharge with a relatively constant pressure during the entire discharge operation. Additionally, the elastic constant for the bladder material slowly degrades with age and use so that the bladder loses some elasticity over time. In the case of a spring-loaded wall type pressure chamber, the spring relaxes over time and therefore performance drops.
Additionally, it is difficult to provide a single elastic constant for the bladder or spring constant for a sprung -walled chamber that allows for ease of use for both younger children, who have less strength to overcome the spring or elastic force to charge the pressure chamber, as well as higher performance for older children and teens who can apply more pumping force.